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Re: [TCLUG:21970] Should DSL or Cable modem
only to lower it I would think, not to increase it.
Tom Veldhouse
veldy@veldy.net
----- Original Message -----
From: "Adam Maloney" <adamm@sihope.com>
To: <tclug-list@mn-linux.org>
Sent: Tuesday, October 03, 2000 11:01 AM
Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> I think it's more commonly used to override the server's default:
>
> man dhcpd:
> ...
> It is possible to specify two lease lengths: the default
> length that will be assigned if a client doesn't ask for
> any particular lease length, and a maximum lease length.
>
> You can request a lease time such that SERVER DEFAULT < requested lease <
> max lease.
>
> Poorly configured DHCP servers that use the default of one day aren't
> optimal. Really when you setup the server you should define the default
> lease time that makes sense (the manpage has an example, an office
> environment where machines aren't added/removed frequently could be a
> month or more, whereas a test environment where machines are just powered
> on, tested, and shipped out could be 30mins). Then specify a max_time so
> clients that are very static (the admin's workstation, for instance) can
> request a much longer lease time.
>
> Anyways, it must have some use otherwise Vix would've removed it. I'd
> rather have the option than not have it.
>
> Adam Maloney
> Systems Administrator
> Sihope Communications
>
> On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
>
> > That is interesting. However, I have never seen a server configuration
that
> > didn't have a lease time specified in it - so in practice, it is
probably
> > meaningless to request a given lease time.
> >
> > Tom Veldhouse
> > veldy@veldy.net
> >
> > ----- Original Message -----
> > From: "Adam Maloney" <adamm@sihope.com>
> > To: <tclug-list@mn-linux.org>
> > Sent: Tuesday, October 03, 2000 10:45 AM
> > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> >
> >
> > > man dhcpcd...
> > >
> > > -l leasetime
> > > Specifies (in seconds) the recommended lease time
> > > to the server. (Note that the server can override
> > > this value if it sees fit). This value is used in
> > > the DHCP_DISCOVER message. The default is infinite
> > > (0xffffffff).
> > >
> > > By default the client will request infinity, and the server will send
it's
> > > configured default lease time back in the Offer. You can't force it
from
> > > the client side, the server always wins (just like Awk!)
> > >
> > > Adam Maloney
> > > Systems Administrator
> > > Sihope Communications
> > >
> > > On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
> > >
> > > > He seemed to be talking about changing the lease time in the already
> > > > negotiated lease file. I wasn't aware you could even configure DHCP
> > clients
> > > > to ask for a given release interval. I never saw such an option
when
> > > > setting up DHCP client.
> > > >
> > > > Tom Veldhouse
> > > > veldy@veldy.net
> > > >
> > > > ----- Original Message -----
> > > > From: "Adam Maloney" <adamm@sihope.com>
> > > > To: <tclug-list@mn-linux.org>
> > > > Sent: Tuesday, October 03, 2000 10:23 AM
> > > > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> > > >
> > > >
> > > > > No, if he tells the client to ask for a lease time of 3 weeks, the
> > client
> > > > > sends that during the negotiation. The server can reject that
lease
> > time
> > > > > if it's too long with a NACK followed by another OFFER with a more
> > > > > plausible lease time.
> > > > >
> > > > > Maybe I mis-understood what he said though. Did he just change
the
> > lease
> > > > > time in the file that dhcpcd writes with the state information?
> > That's
> > > > > bad. Really bad. If he changes the lease time there then the
server
> > > > > doesn't know about it. Then you're right, if he sets that to 3
weeks
> > and
> > > > > the initial lease was for 2 weeks, then after 2 weeks the server
will
> > be
> > > > > expecting a renew that it will never get. It'll assume the
client's
> > gone
> > > > > and put the IP back into the pool. If a new subscriber came along
> > they
> > > > > could snag up "his" IP legitimately. Then after a week his client
> > will
> > > > > try to renew the IP and the server will NACK it because it's
already
> > been
> > > > > leased. Not to mention all the problems he'd have with IP
conflicts.
> > > > >
> > > > > Adam Maloney
> > > > > Systems Administrator
> > > > > Sihope Communications
> > > > >
> > > > > On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
> > > > >
> > > > > > Right. But if he changes the lease time to 3 weeks, but the
server
> > is
> > > > > > configured for 2 weeks, there may be a 1 week period where two
> > different
> > > > > > computers share the same IP address, because somebody else has
> > received
> > > > the
> > > > > > IP address, and his computer will not ask to renew the old IP
> > address
> > > > for
> > > > > > another week yet.
> > > > > >
> > > > > > Tom Veldhouse
> > > > > > veldy@veldy.net
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: "Adam Maloney" <adamm@sihope.com>
> > > > > > To: <tclug-list@mn-linux.org>
> > > > > > Sent: Tuesday, October 03, 2000 9:30 AM
> > > > > > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> > > > > >
> > > > > >
> > > > > > > Well if his dhcp client sends a Renew request to the server,
the
> > > > server
> > > > > > > can reject it. The dhcp client will then just ask for a new
IP.
> > As
> > > > long
> > > > > > > as he doesn't muck with the client (or bypass it altogether
and
> > just
> > > > > > > statically configure it) he can't cause any trouble. The
server
> > can
> > > > > > > always reject renew requests if the address has already bgeen
> > > > reassigned.
> > > > > > > I don't think there's anything he can do to the configuration
of
> > the
> > > > > > > client that could screw anything up, I think he'd have to
modify
> > the
> > > > > > > source.
> > > > > > >
> > > > > > > If the IP has already been leased to someone else, and his
client
> > asks
> > > > for
> > > > > > > that IP (in a renew request) the server will send a NACK back,
> > then an
> > > > > > > OFFER with a new IP.
> > > > > > >
> > > > > > > In any case, by changing the lease time you're probably not
> > helping
> > > > > > > yourself at all. As soon as the lease ends your client will
send
> > a
> > > > renew
> > > > > > > request back to the server and you'll get your IP back
anyways.
> > The
> > > > lease
> > > > > > > time just dictates how long before you have to renew again,
but if
> > the
> > > > > > > server reboots you may be SOL. I believe ISC's stores the
lease
> > > > > > > information in /var somewhere so if the server restarts it'll
know
> > who
> > > > has
> > > > > > > what leased...but I don't know about whatever DHCP server
they're
> > > > using.
> > > > > > > If it's Microsoft's it'll probably explode or something...
> > > > > > >
> > > > > > > Adam Maloney
> > > > > > > Systems Administrator
> > > > > > > Sihope Communications
> > > > > > >
> > > > > > > On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
> > > > > > >
> > > > > > > > Yeah, and that somebody is going to be pissed if they find
out
> > that
> > > > > > somebdoy
> > > > > > > > is using their IP and causing them to have problems with
there
> > cable
> > > > > > modem.
> > > > > > > > Most users are not going to know what the problem is and
they
> > are
> > > > simply
> > > > > > > > going to call MediaOne and complain. If MediaOne then finds
> > this,
> > > > one
> > > > > > had
> > > > > > > > better watch out, because suddenly the support costs are
larger
> > than
> > > > the
> > > > > > > > profits that they are making off of the trouble causing
> > individual.
> > > > > > > >
> > > > > > > > Tom Veldhouse
> > > > > > > > veldy@veldy.net
> > > > > > > >
> > > > > > > > ----- Original Message -----
> > > > > > > > From: "Adam Maloney" <adamm@sihope.com>
> > > > > > > > To: <tclug-list@mn-linux.org>
> > > > > > > > Sent: Tuesday, October 03, 2000 9:17 AM
> > > > > > > > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> > > > > > > >
> > > > > > > >
> > > > > > > > > Well if they ran ISC's DHCPd they can set Max-Lease-Time,
> > which is
> > > > the
> > > > > > > > > maximum amount of time a given address will be leased for.
> > That's
> > > > not
> > > > > > to
> > > > > > > > > say that when the lease expires you won't renew and get it
> > again,
> > > > but
> > > > > > if
> > > > > > > > > you don't renew right away someone else will probably get
it.
> > > > > > > > >
> > > > > > > > > Adam Maloney
> > > > > > > > > Systems Administrator
> > > > > > > > > Sihope Communications
> > > > > > > > >
> > > > > > > > > On Mon, 2 Oct 2000, Eric F Crist wrote:
> > > > > > > > >
> > > > > > > > > > Trust me, it works. I've gotten calls from TW and
MediaDumb
> > > > (aka
> > > > > > ATT)
> > > > > > > > and
> > > > > > > > > > they've not been able to stop it, short of pulling the
> > provision
> > > > for
> > > > > > > > your MAC
> > > > > > > > > > address.
> > > > > > > > > >
> > > > > > > > > > But, there are ways around that too. =P
> > > > > > > > > >
> > > > > > > > > > On Mon, 02 Oct 2000, you wrote:
> > > > > > > > > > >
> > > > > > > > > > > Thats *only* if the other end accepts such bad things.
> > > > > > > > > > >
> > > > > > > > > > > AFAIK, you can setup ISC to ignore it.
> > > > > > > > > > >
> > > > > > > > > > > * Eric F Crist <ecrist@ardent-hacker.net> [001002
21:37]:
> > > > > > > > > > > > After a little more research (I had a brain-fart)
the
> > file,
> > > > on a
> > > > > > > > freebsd =
> > > > > > > > > > > system
> > > > > > > > > > > > is /var/db/dhclient.leases
> > > > > > > > > > > >=20
> > > > > > > > > > > > This file is realatively simple and straightfoward.
For
> > > > > > information
> > > > > > > > on y=
> > > > > > > > > > > our
> > > > > > > > > > > > box, type man dhclient.leases
> > > > > > > > > > > >=20
> > > > > > > > > > > > If you have questions or comments, feel free to
email
> > me.
> > > > > > > > > > > >=20
> > > > > > > > > > > >=20
> > > > > > > > > > > >=20
> > > > > > > > > > > > Au Contrair on the static IP. If you're into the
> > computer
> > > > > > hacking
> > > > > > > > side of
> > > > > > > > > > > > things, you can simply change your lease on the IP
to
> > never
> > > > > > expire.
> > > > > > > > Ther=
> > > > > > > > > > > e's a
> > > > > > > > > > > > file located on your hard drive that actually sets
your
> > > > lease.
> > > > > > This
> > > > > > > > is
> > > > > > > > > > > > overwritten at the time of renewal by the DHCP
server.
> > I
> > > > have
> > > > > > done
> > > > > > > > this =
> > > > > > > > > > > myself
> > > > > > > > > > > > and know others who do it successfully. Maybe not a
> > legit
> > > > > > static
> > > > > > > > IP, but=
> > > > > > > > > > > until
> > > > > > > > > > > > they find out, who cares?=20
> > > > > > > > > > > >=20
> > > > > > > > > > > > On Mon, 02 Oct 2000, you wrote:
> > > > > > > > > > > > > Disadvantages to cable modem (from my point of
view)
> > > > > > > > > > > > > - no static IPs, may be coming soon though
> > > > > > > > > > > > > - no services on your machine, or you get booted
> > > > > > > > > > > > >=20
> > > > > > > > > > > > > Advantages to cable modem
> > > > > > > > > > > > > - much faster
> > > > > > > > > > > > >=20
> > > > > > > > > > > > > I got this information from the Time Warner sales
rep
> > and
> > > > the
> > > > > > tech
> > > > > > > > rep =
> > > > > > > > > > > that
> > > > > > > > > > > > > showed up at my apartment complex trying to get
> > > > subscribers.
> > > > > > > > > > > > >=20
> > > > > > > > > > > > > --=20
> > > > > > > > > > > > > Jon Schewe | http://eggplant.mtu.net/~jpschewe
> > > > > > > > > > > > > For I am convinced that neither death nor life,
> > neither
> > > > > > angels=20
> > > > > > > > > > > > > nor demons, neither the present nor the future,
nor
> > any=20
> > > > > > > > > > > > > powers, neither height nor depth, nor anything
else in
> > > > all=20
> > > > > > > > > > > > > creation, will be able to separate us from the
love of
> > God
> > > > > > that=20
> > > > > > > > > > > > > is in Christ Jesus our Lord. - Romans 8:38-39
> > > > > > > > > > > > >=20
> > > > > > > > > > > > >=20
> > > > > > > > > > > >
> > > > > > > >
> > > >
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> > > > > > > > > > > > Eric F Crist
> > > > > > > > > > > > System Administrator
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